¨
the high temperature conditions needed to prepare the metal
compounds.
10 C. G. Coates, J. Olofsson, M. Coletti, J. J. McGarvey, B. Onfelt, B.
Lincoln, B. Norde´n, E. Tuite, P. Matousek and A. W. Parker, J. Phys.
Chem. B, 2001, 105, 12653.
The second important observation is that the absorption spectra
of the free ligands are very dependent on the substitution pattern.
Importantly, with increasing aryl character the ligand centred p–
p* transition of the LR ligand moves to lower energy and overlaps
considerably with the MLCT transition. This effect has two
potentially important consequences; one relates to the application
of the ruthenium dppz complexes as luminescent sensors, in that
higher extinction coefficients in the visible region will result in a
better sensor (ruthenium complex) to analyte (for instance DNA)
ratio.
In addition this shift may affect the so called “dark state”
of the dppz molecule.35 The importance of intraligand electron
transfer, from the initially populated bpy 1MLCT to the phenazine
based 3MLCT for explaining the unusual light switch mechanism
observed for the ruthenium dppz complexes has recently been
emphasised by Batista and Martin.36 Expansion of the aromatic
frame as evident in L2 to L4 may be expected to influence the rate
constants for this process and therefore lead to new insights into
this phenomenon.
11 G. Pourtois, D. Beljonne, C. Moucheron, S. Schumm, A. Kirsch-De
Mesmaeker, R. Lazzaroni and J.-L. Bredas, J. Am. Chem. Soc., 2004,
126, 683.
12 D. A. McGovern, A. Selmi, J. E. O’Brien, J. M. Kelly and C. Long,
Chem. Commun., 2005, 1402.
13 W. Chen, C. Turro, L. A. Friedman, J. K. Barton and N. J. Turro,
J. Phys. Chem. B, 1997, 101, 6995.
14 P. Aguirre, R. Lo´pez, D. Villagra, I. Azocar-Guzman, A. J. Pardey and
S. A. Moya, Appl. Organomet. Chem., 2003, 17, 36.
15 N. J. Lundin, P. J. Walsh, S. L. Howell, J. J. McGarvey, A. G. Blackman
and K. C. Gordon, Inorg. Chem., 2005, 44, 3551 and references cited
therein.
16 M. K. Kuimova, W. Z. Alsindi, J. Dyer, D. C. Grills, O. S. Jina, P.
Matousek, A. W. Parker, P. Portius, X. Zhong Sun, M. Towrie, C.
Wilson, J. Yang and M. W. George, Dalton Trans., 2003, 3996.
17 P. Y. Chen and T. J. Meyer, Chem. Rev., 1998, 98, 1439.
18 E. Amouyal, A. Homsi, J.-C. Chambron and J.-P. Sauvage, J. Chem.
Soc., Dalton Trans., 1990, (6), 1841.
19 E. M. Kober and T. J. Meyer, Inorg. Chem., 1982, 21, 3967.
20 C. G. Coates, P. Callaghan, J. J. McGarvey, J. M. Kelley, P. E. Kruger
and M. E. Higgins, J. Raman Spectrosc., 2000, 31, 283.
21 J.-C. Chambron and J.-P. Sauvage, Chem. Phys. Lett., 1991, 182, 603.
¨
22 J. Olofsson, B. Onfelt, B. Lincoln, B. Norde´n, P. Matousek, A. W.
Parker and E. Tuite, J. Inorg. Biochem., 2002, 91, 286.
23 V. W.-W. Yam, V. W.-M. Lee, F. Ke and K.-W. M. Siu, Inorg. Chem.,
1997, 36, 2124.
24 J. K. Barton, L. A. Basile, A. Danishefsky and A. Alexandrescu, Proc.
Natl. Acad. Sci. U. S. A., 1984, 81, 1961.
Acknowledgements
25 P. P. Pellegrini and J. R. Aldrich-Wright, Dalton Trans., 2003, 176.
26 S. Rau, B. Scha¨fer, A. Gru¨ßing, S. Schebesta, K. Lamm, J. Vieth, H.
Go¨rls, D. Walther, M. Rudolph, U. W. Grummt and E. Birkner, Inorg.
Chim. Acta, 2004, 357, 4496.
27 G. W. H. Cheeseman, J. Chem. Soc. C, 1962, 1170.
28 COLLECT, Data Collection Software, Nonius B.V., Netherlands, 1998.
29 Z. Otwinowski and W. Minor, Processing of X-Ray Diffraction
Data Collected in Oscillation Mode, in Methods in Enzymology,
vol. 276. Macromolecular Crystallography, Part A, ed. C. W. Carter
and R. M. Sweet, Academic Press, 1997, pp. 307–326.
30 G. M. Sheldrick, Acta Crystallogr. Sect. A, 1990, 46, 467.
31 G. M. Sheldrick, SHELXL-97 (Release 97-2), University of Go¨ttingen,
Germany, 1997.
Financial support by the DFG (SFB 436) is gratefully acknowl-
edged. S.R. acknowledges financial support by the DFG (RA
1017/1-1 and 1-2). W.H. would like to thank Enterprise Ireland
(Grant Number SC/2003/74) for financial support. We would
like to thank Professor D. Walther for helpful discussions and
encouragement.
References
1 J. K. Barton, A. T. Danishefsky and J. M. Goldberg, J. Am. Chem. Soc.,
1984, 106, 2172.
2 J. M. Kelly, A. B. Tossi, D. J. McConnell and C. OhUigin, Nucleic Acids
Res., 1985, 13, 6017.
3 J. K. Barton, J. M. Goldberg, C. V. Kumar and N. J. Turro, J. Am.
Chem. Soc., 1986, 108, 2018.
32 R. Passalacqua, F. Loiseau, S. Campagna, Y.-Q. Fang and G. S. Hanan,
Angew. Chem., Int. Ed., 2003, 42, 1608.
33 C. J. Aspley and J. A. Gareth Williams, New J. Chem., 2001, 25, 1136.
34 J. Rusanova, S. Decurtins, E. Rusanov, H. Stoeckli-Evans, S. Delahaye
and A. Hauser, Dalton Trans., 2002, 4318.
4 C. Hiort, B. Norde´n and A. Rodger, J. Am. Chem. Soc., 1990, 112,
1971.
5 A. E. Friedman, J. C. Chambron, J.-P. Sauvage, N. J. Turro and J. K.
Barton, J. Am. Chem. Soc., 1990, 112, 4960.
6 B. Lincoln, A. Broo and B. Norde´n, J. Am. Chem. Soc., 1996, 118, 2644.
7 C. G. Coates, L. Jacquet, J. J. McGarvey, S. E. J. Bell, A. H. R. Al-Obaidi
and J. M. Kelly, J. Am. Chem. Soc., 1997, 119, 7130.
8 I. D. Greguric, J. R. Aldrich-Wright and J. G. Collins, J. Am. Chem.
Soc., 1997, 119, 3621.
35 Matthew K. Brennaman, T. J. Meyer and J. M. Papanikolas, J. Phys.
Chem. A, 2004, 108, 9938.
36 E. R. Batista and R. L. Martin, J. Phys. Chem. A, 2005, 109, 3128.
37 K. O’Donoghue, J. C. Penedo, J. M. Kelly and P. E. Kruger, Dalton
Trans., 2005, 1123.
38 R. S. Nair, B. M. Cullum and C. J. Murphy, Inorg. Chem., 1997, 36,
962.
39 J. R. Schoonover, W. D. Bates and T. J. Meyer, Inorg. Chem., 1995, 34,
6421.
9 Y. Jenkins, A. E. Friedman, N. J. Turro and J. K. Barton, Biochemistry,
1992, 31, 10809.
40 See for instance S. Fantacci, F. DeAngelis, A. Sgamellotti and N. Re,
Chem. Phys. Lett., 2004, 396, 43–48.
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